Synchronization method, communication handover method, radio network and node

ABSTRACT

A synchronization method, a communication handover method, a radio network, and a RAN node are disclosed. The interface information synchronization method includes determining whether a condition for initiating interface information update is fulfilled. Information about the S1 interface between the RAN node and the core network node, is sent. In addition, or alternatively, information about the X2 interface between the RAN node and the neighboring RAN node is sent to the neighboring RAN node if the condition for initiating interface information update fulfilled.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/540,221, filed on Jul. 2, 2012, which is a continuation of U.S.patent application Ser. No. 12/609,363, filed on Oct. 30, 2009, now U.S.Pat. No. 8,249,020. The U.S. patent application Ser. No. 12/609,363 is acontinuation of co-pending International Application No.PCT/CN2008/070789, filed Apr. 24, 2008, which designated the UnitedStates and was not published in English, and which claims priority toChinese Application No. 200710103636.9, filed Apr. 30, 2007. All of theabove described applications are incorporated herein by reference.

TECHNICAL FIELD

The present application relates generally to the communication field,and in particular, to an interface information synchronization method, acommunication handover method, a radio network, and a Radio AccessNetwork (RAN) node.

BACKGROUND

The Long Term Evolution/System Architecture Evolution (LTE/SAE) networksystem project is the biggest new technology development projectlaunched by the 3rd Generation Partnership Project (3GPP) in recentyears. The core of such a technology is Orthogonal Frequency DivisionMultiplexing (OFDM)/Frequency Division Multiple Access (FDMA), andtherefore, such a technology has some 4^(th) Generation (4G) featuresand is regarded as a quasi-4G technology.

FIG. 1 shows an architecture of an LTE/SAE in the conventional art. TheLTE/SAE network system includes an evolved Node B (eNB) and the MobilityManagement Entity/Serving System Architecture Evolution Gateway(MME/SGW) that manages the RAN nodes. The interface between the MME/SGWand the eNB is an S1 interface, and the interface between eNBs is an X2interface.

In the current LTE, the communication handover process falls into twotypes: handover from a source eNB to a target eNB through an X2interface; and handover from a source eNB to a target eNB through an S1interface, as described below.

Handover through an X2 interface: In the handover process, the sourceeNB and the target eNB are governed by the same MME; the MME isunchanged; and the source eNB sends a Handover Request message to thetarget eNB through an X2 interface to perform handover. In this case,the handover process involves no MME, and is known as handover throughan X2 interface. The handover performed through an X2 interface involvesuse of an S1 interface.

Handover through an S1 interface: When the MME involved in the handoverprocess changes, namely, when the source eNB and the target eNB are notgoverned by the same MME, the source eNB needs to send a HandoverRequest message through an S1 interface, which is known as handoverthrough an S1 interface.

When an eNB initiates handover, as regards how to select either of theforegoing handover methods, the conventional art puts forward thefollowing eNB handover selection method:

A. If no X2 interface exists, the handover is performed through the S1interface.

B. If the handover configured in the source eNB to the neighboringtarget eNB is performed through an S1 interface, the handover isperformed through the S1 interface.

In this method, a static table is reserved in the source eNB first, anda decision is made about whether to perform handover through an S1interface or an X2 interface according to the interface connectioninformation related to the neighboring eNB and recorded in the statictable. However, the conventional art describes neither the structure ofsuch a static table nor information about how to use the static table toperform communication handover.

C. If a rejection message is received from the target eNB during the X2interface handover, it indicates that the handover cannot be performedthrough an X2 interface, and therefore, the handover is performedthrough an S1 interface.

In this method, the Handover Request is sent through an X2 interface solong as an X2 interface connection exists. If the target eNB finds itimpossible to perform handover through an X2 interface, for example, ifit is determined that the same MME connection is lacking, the target eNBsends a handover failure message to the source eNB. The handover failuremessage carries the corresponding cause value, and instructs the sourceeNB to send a Handover Require message to the MME again through an S1interface.

In the process of developing the present invention, the inventor findsat least the following defects in the conventional art.

(1) For solution B, the source eNB needs to know the staticconfiguration of the relevant interface of the neighboring eNB. Dataneeds to change with the change of the configuration of the neighboringeNB. Manual modification of the static configuration consumes much timeand effort, and is vulnerable to errors. Besides, the conventional artdescribes neither the structure of the static table nor the informationabout how to use the static table to perform communication handover.

(2) In solution C, for the handover which can be performed only throughthe S1 interface, sending a Handover Request first through the X2interface is necessary, which wastes resources and increases delay.According to the X2 interface handover process in the conventional art,the target eNB can set up air interface resources upon receiving aHandover Request. However, if solution C is applied, the target eNBneeds to judge whether X2 interface handover is practicable afterreceiving a Handover Request, thus increasing futile operations for theX2 interface-enabled handover processes.

SUMMARY

The present invention discloses an interface information synchronizationmethod, a communication handover method, a radio network, and a RANnode, thus improving the efficiency of communication handover.

An interface information synchronization method is disclosed in anembodiment of the present invention. The method includes determiningwhether a condition for initiating interface information update isfulfilled; sending information about an S1 interface between a RAN nodeand a core network node, and/or information about an X2 interfacebetween the RAN node and a neighboring RAN node to the neighboring RANnode if the condition for initiating interface information update isfulfilled.

A communication handover method is disclosed in an embodiment of thepresent invention. The method includes: (1) reading, by a source RANnode, a stored interface handover entries when handover occurs, wherethe interface handover entries include information indicating whetherthe handover can be performed to the target RAN node through an S1interface, and the interface handover entries are obtained according tothe S1 and/or an X2 interface information; and (2) performing thehandover through the S1 interface if the interface handover entriesinclude the information that the handover can be performed to the targetRAN node through the S1 interface; otherwise, performing the handoverthrough the X2 interface.

A communication handover method is disclosed in an embodiment of thepresent invention. The method includes: (1) reading, by a source RANnode, interface information when handover occurs, where the interfaceinformation includes information about whether an X2 interface existsbetween the source RAN node and a target RAN node and/or informationabout whether an S1 interface exists between a serving core network ofthe source RAN node and the RAN node; and (2) performing handoverthrough the X2 interface if the interface information indicates that theX2 interface exists between the source RAN node and the target RAN nodeand/or the S1 interface exists between the serving core network node ofthe source RAN node and the target RAN node; otherwise, performinghandover through the S1 interface.

A radio network is disclosed in an embodiment of the present invention.The radio network includes a first RAN node, a second RAN node, and aserving core network node of the second RAN node.

The first RAN node includes: (1) a judging unit, adapted to judgewhether a condition for initiating interface information update isfulfilled; and (2) a sending unit, adapted to send information about anX2 interface between the first RAN node and the second RAN node and/orinformation about an S1 interface between the first RAN node and theserving core network node to the second RAN node if the condition forinitiating interface information update is fulfilled.

The second RAN node includes: (1) a receiving unit, adapted to receivethe S1 and/or X2 interface information; (2) a handover selecting unit,adapted to search for the interface information; if finding informationabout the X2 interface between the first RAN node and the second RANnode and determining that an S1 interface connection exists between theserving core network node and the first RAN node according to the S1interface information, initiate a handover operation to the first RANnode through the X2 interface; otherwise, initiate the handoveroperation to the first RAN node through the S1 interface.

A RAN node is disclosed in an embodiment of the present invention. TheRAN node includes: (1) a judging unit, adapted to judge whether acondition for initiating interface information update is fulfilled; and(2) a sending unit, adapted to send information about an X2 interfacebetween the RAN node and a neighboring RAN node and/or information aboutan S1 interface between the RAN node and a core network node to theneighboring RAN node if the judging unit determines that the conditionfor initiating interface information update is fulfilled.

A RAN node is disclosed in an embodiment of the present invention. TheRAN node includes: (1) a receiving unit, adapted to receive S1 and/or X2interface information from a neighboring RAN node; (2) a processingunit, adapted to configure or update the interface information of theneighboring RAN node after the receiving unit receives the S1 and/or X2interface information; and (3) a handover selecting unit, adapted tosearch the processing unit for the interface information; if finding theinformation about the X2 interface between the RAN node and theneighboring RAN node as well as the information about the S1 interfacebetween a serving core network node of the RAN node and the neighboringRAN node, select the X2 interface for initiating a handover operation tothe neighboring RAN node; otherwise, select the S1 interface forinitiating the handover operation to the neighboring RAN node.

A RAN node is disclosed in an embodiment of the present invention. TheRAN node includes: (1) a receiving unit, adapted to receive S1 and/or X1interface information from a neighboring RAN node; (2) an interfaceinformation generating unit, adapted to judge whether a core networknode of the RAN node serving as a source node is the same as a corenetwork node of the neighboring RAN node serving as a target nodeaccording to the interface information of the RAN node and the S1 and/orX1 interface information received by the receiving unit; and generatehandover information indicative of handing over to the target RAN nodethrough an S1 interface if the core network node of the RAN node servingas the source node is not same as the core network node of theneighboring RAN node serving as the target node; and (3) a handoverselecting unit, adapted to search for the handover information generatedby the interface information generating unit during the handover; iffinding the information about the handover performed through the S1interface to the target RAN node, select the S2 interface for initiatinga handover operation to the neighboring RAN node; otherwise, select theX2 interface for initiating a handover operation to the neighboring RANnode.

As described above, in an embodiment of the present invention, theinformation about the S1 interface between the RAN node and the corenetwork node, and/or information about the X2 interface between the RANnode and the neighboring RAN node is sent to the neighboring RAN node ifthe condition is fulfilled. When the neighboring RAN node hands over tothe RAN node, the neighboring RAN node can determine whether an S1interface exists between the neighboring RAN node itself and the corenetwork according to its own S1 interface information and the receivedS1 interface information, and can accurately determine the interfaceavailable for handover according to the received X2 interfaceinformation. Therefore, the proper interface is selected accurately andquickly, the trouble of determining whether the X2 interface isavailable for handover in the case of unawareness of the interfaceinformation in the conventional art is avoided, the handover efficiencyis improved, and the system load is reduced.

In another embodiment of the present invention, the interfaceinformation or the interface handover table is read when handover isperformed; a proper interface is selected for handover according to theinterface handover requirement recorded in the interface handover tableor according to the interface which is determined as available forhandover in view of the interface information. The determining mode is:A Handover Request is sent through the X2 interface if the interfaceinformation indicates that an X2 interface exists between the source RANnode and the target RAN node and/or an S1 interface exists between theserving core network node of the source RAN node and the target RANnode; otherwise, the Handover Request is sent through an S1 interface.Therefore, the proper interface is selected accurately and quickly. Thetrouble of determining whether the X2 interface is available forhandover in the case of unawareness of the interface information in theconventional art is avoided, the handover efficiency is improved, andthe system load is reduced.

In another embodiment of the present invention, a judging unit judgeswhether the interface information needs update, and a sending unit sendsthe interface information to the neighboring RAN node to synchronize theinterface information. The handover selecting unit of the neighboringRAN node may select a proper interface for handover according tointerface handover requirement recorded in the interface handover table,or according to the interface available for handover determined in viewof the interface information. The determining mode is: A HandoverRequest is sent through the X2 interface if the interface informationindicates that an X2 interface exists between the source RAN node andthe target RAN node and/or an S1 interface exists between the servingcore network node of the source RAN node and the target RAN node;otherwise, the Handover Request is sent through an S1 interface.Therefore, the proper interface is selected accurately and quickly. Thetrouble of determining whether the X2 interface is available forhandover in the case of unawareness of the interface information in theconventional art is avoided, the handover efficiency is improved, andthe system load is reduced.

In another embodiment of the present invention, interface informationmay be transmitted between neighboring RAN nodes. Therefore, the RANnode knows the interface information of the neighboring RAN node, andsuch interface information is a basis for selecting a specific interfacefor handover. The two technical solutions can work together to select aproper interface for handover accurately and efficiently, and reducesystem load.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a structure of an LTE/SAE network in the conventional art;

FIG. 2 is a flowchart of a communication handover method in anembodiment of the present invention;

FIG. 3 shows X2 and S1 interface connections in an LTE/SAE network;

FIG. 4 is a flowchart of interface information synchronization method inanother embodiment of the present invention;

FIG. 5 is a flowchart of a communication handover method in anembodiment of the present invention;

FIG. 6 is a signaling flowchart of interface information synchronizationmethod in another embodiment of the present invention;

FIG. 7 is a signaling flowchart of interface information synchronizationmethod in another embodiment of the present invention;

FIG. 8 is a signaling flowchart of interface information synchronizationmethod in another embodiment of the present invention;

FIG. 9 shows a structure of a radio network in an embodiment of thepresent invention; and

FIG. 10 shows a structure of a RAN node in an embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

A communication handover method is disclosed in an embodiment of thepresent invention. The method includes a number of steps.

A RAN node stores the information about the X2 interface between the RANnode and a neighboring RAN node, and/or the information about the S1interface between the neighboring RAN node and a core network node. Theinformation about the X2 interface or the S1 interface may be interfaceconfiguration information and/or interface state information. Theconfiguration information and/or state information constitute aconfiguration table (S1 or X2 interface configuration table of the RANnode).

If the S1 or X2 interface configuration/state of the RAN node changes,the RAN node sends the changed S1 or X2 interface configuration/stateinformation to the neighboring RAN node, notifying the neighboring RANnode to modify the corresponding S1 or X2 interface configuration table.

Therefore, RAN nodes in the communication network have the latest S1 orX2 interface configuration table. When handover occurs, the source RANnode searches for the configuration information of the target RAN nodein the S1 or X2 interface configuration table. A procedure is used toperform handover from a source RAN node to a target RAN node using X2interface when S1 interface exists between the target RAN node and aserving core network node of the source RAN node. Otherwise the S1-basedhandover procedure is used.

A communication handover method is disclosed in an embodiment of thepresent invention. The method includes a number of steps.

The S1 interface information between the RAN node and the core networknode is transmitted to the neighboring RAN node through an X2 interface.The neighboring RAN node generates an S1 interface handover tableaccording to the S1 interface information of the neighboring RAN nodeitself and the received S1 interface information, where the S1 interfacehandover table indicates whether the handover is necessarily performedthrough the S1 interface. The S1 interface handover table is storeddynamically. Whenever the S1 interface configuration/state of theneighboring RAN node changes, the change is notified to the RAN nodethrough the X2 interface. The RAN node modifies the S1 interfacehandover table according to the S1 interface information. When handoveroccurs, the source RAN node searches the S1 interface handover table forthe target RAN node. If finding the target RAN node, the source RAN nodeselects the S1 interface for handover; otherwise, the source RAN nodeselects the X2 interface for handover.

According to the method disclosed in the embodiment of the presentinvention, the RAN nodes may exchange S1 interface information and/or X2interface information automatically through automatic configuration ofthe network. More specifically, the interface information for exchangingis: both S1 interface information and X2 interface information; only S1interface information; or only X2 interface information.

The RAN node may be an eNB, and the core network node may be an MME.

An interface information synchronization method is disclosed in anembodiment of the present invention. The method includes: (1)determining whether a condition for initiating interface informationupdate is fulfilled; (2) sending information about the S1 interfacebetween the RAN node and the core network node, and/or information aboutthe X2 interface between the RAN node and the neighboring RAN node tothe neighboring RAN node if the condition for initiating interfaceinformation update is fulfilled; (3) receiving the S1 and/or X2interface information; and (4) configuring or updating the interfaceinformation of the neighboring RAN node according to the received S1and/or X2 interface information.

In the embodiment described above, the S1 and/or X2 interfaceinformation of the RAN node is sent to the neighboring RAN node when thecondition is fulfilled. When the neighboring RAN node hands over to theRAN node, the neighboring RAN node can determine whether an S1 interfaceexists between the neighboring RAN node itself and the core networkaccording to its own S1 interface information and the received S1interface information, and can accurately determine the interfaceavailable for handover according to the received X2 interfaceinformation. Therefore, the proper interface is selected accurately andquickly, the trouble of determining whether the X2 interface isavailable for handover in the case of unawareness of the interfaceinformation in the conventional art is avoided, the handover efficiencyis improved, and the system load is reduced.

In the communication handover method disclosed in the embodiment of thepresent invention, when handover occurs, the source RAN node reads thestored interface handover table (the interface handover table includesthe information indicating whether the handover can be performed throughan S1 interface to the target RAN node). The source RAN node performshandover through the S1 interface if the interface handover tableindicates that the handover can be performed through the S1 interface tothe target RAN node; otherwise, the source RAN node performs handoverthrough the X2 interface. Therefore, the proper interface is selectedaccurately and quickly. The trouble of determining whether the X2interface is available for handover in the case of unawareness of theinterface information in the conventional art is avoided, the handoverefficiency is improved, and the system load is reduced.

In the communication handover method disclosed in the embodiment of thepresent invention, the source RAN node reads interface information whenhandover occurs, the interface information includes the informationabout whether an X2 interface exists between the source RAN node and thetarget RAN node and/or the information about whether an S1 interfaceexists between the serving core network node of the source RAN node andthe target RAN node. The source RAN node performs handover through theX2 interface if the interface information indicates that an X2 interfaceexists between the source RAN node and the target RAN node and/or an S1interface exists between the serving core network node of the source RANnode and the target RAN node; or else performs handover through the S1interface. Therefore, the proper interface is selected accurately andquickly. The trouble of determining whether the X2 interface isavailable for handover in the case of unawareness of the interfaceinformation in the conventional art is avoided, the handover efficiencyis improved, and the system load is reduced.

In the communication handover method disclosed in the embodiment of thepresent invention, the interface information or the interface handovertable is read when handover occurs, a proper interface is selected forhandover according to the interface handover requirement recorded in theinterface handover table or according to the interface which isdetermined as available for handover in view of the interfaceinformation. The determining mode is: A Handover Request is sent throughthe X2 interface if the interface information includes the informationabout the X2 interface exists between the source RAN node and the targetRAN node and the information about the S1 interface exists between theserving core network node of the source RAN node and the target RANnode; otherwise, the Handover Request is sent through an S1 interface.Therefore, the proper interface is selected accurately and quickly. Thetrouble of determining whether the X2 interface is available forhandover in the case of unawareness of the interface information in theconventional art is avoided, the handover efficiency is improved, andthe system load is reduced.

In order to make the technical solution, objectives and merits of thepresent invention clearer, the communication handover method under thepresent invention is detailed below by reference to FIG. 2.

FIG. 2 is a flowchart of a communication handover method in anembodiment of the present invention. The process includes at least thefollowing steps.

Step 201: The source RAN node reads S1 and X2 interface information whenhandover occurs, the interface information includes the informationabout whether an X2 interface exists between the source RAN node and thetarget RAN node and/or the information about whether an S1 interfaceexists between the serving core network node of the source RAN node andthe target RAN node.

As described above, the S1 and the X2 interface information may exist inthe form of S1 and X2 interface configuration table, and may be storedon the source RAN node. Taking the LTE/SAE network shown in FIG. 3 as anexample, RAN node 1 is adjacent to RAN nodes 2 and 3 in the network, andan X2 interface exists between them.

Table 1 is an exemplary structure of an S1 or X2 interface configurationtable in the network.

For example, in FIG. 3, RAN node 1 is adjacent to RAN nodes 2 and 3, andan X2 interface exists between them. RAN node 1 may store the followingtable.

TABLE 1 S1 or X2 interface configuration table of RAN node 1 corenetwork core network core network RAN node node 1 node 2 node 3 RAN node0 1 1 2 RAN node 0 0 1 3

The first column of the table is the information about the neighboringRAN node. The first column includes RAN node 2 and RAN node 3. An X2interface exists between RAN node 1 and RAN nodes 2 and 3. If the columnhas no name of a RAN node, it indicates that no X2 interface existsbetween RAN node 1 and the RAN node.

The first row of the table indicates the relevant core network nodes,and the content below the second row indicates whether an S1 interfaceexists between each neighboring RAN node and the relevant core networknode. “1” indicates that an S1 interface exists between a RAN node andthe relevant core network node; and “0” indicates that no S1 interfaceexists between them. The foregoing table reveals a number of facts. AnS1 interface exists between RAN node 2 and core network nodes 2 and 3,but no S1 interface exists between RAN node 2 and core network node 1.In addition, an S1 interface exists between RAN node 3 and core networknode 3, but no S1 interface exists between RAN node 3 and core networknode 1 or 2.

In this case, when the source RAN node knows existence of an S1interface between the source RAN node and the relevant core networknode, according to the second row and the content below the second row,the source RAN node may infer whether an S1 interface exists between theserving core network of the source RAN node and other neighboring RANnodes. For example, if RAN node 2 and the serving core network node 2 ofRAN node 1 correspond to the position “1” in the table but RAN node 1already knows that an S1 interface exists between RAN node 1 and corenetwork node 2, it is inferred that an S1 interface exists between RANnode 1 and the serving core network node 2 of RAN node 2.

Obviously, the first column of the table indicates whether an X2interface exists between the source RAN node and other neighboring RANnodes. The second row of the table indicates whether an S1 interfaceconnection exists between the neighboring RAN node and the core networknode. The source RAN node may infer whether an S1 interface existsbetween the serving core network node of the source RAN node and theneighboring RAN node according to the S1 interface information of thesource RAN node and the S1 interface information below the second row inthe table.

Likewise, other neighboring RAN nodes also store similar configurationtables for communication handover. Table 2 and Table 3 are examples.

TABLE 2 S1 or X2 interface configuration table of RAN node 2 Corenetwork Core network Core network RAN node node 1 node 2 node 3 RAN node1 1 0 1

TABLE 3 S1 or X2 interface configuration table of RAN node 3 corenetwork core network core network RAN node node 1 node 2 node 3 RAN node1 1 0 1

Nevertheless, the RAN node may also add its own S1 interface informationinto the first row of the foregoing configuration table. The second rowand the content below it are the information about the neighboring RANnode, as shown in Table 4.

TABLE 4 S1 or X2 interface configuration table of RAN node 1 Corenetwork Core network Core network RAN node node 1 node 2 node 3 RAN node1 1 0 1 RAN node 0 1 1 2 RAN node 0 0 1 3

In this way, according to the information in Table 4, when RAN node 1serves as a source RAN node, it is easy to determine whether an S1interface exists between the source RAN node and a core network node,and whether an S1 interface exists between another neighboring RAN nodeand the core network node.

When handover needs to occur on the source RAN node, the source RAN nodereads the S1 and X2 interface configuration table stored locally first,and then performs the following steps.

Step 202: If the interface configuration table includes the informationabout the X2 interface exists between the source RAN node and the targetRAN node and the information about the S1 interface exists between theserving core network node of the source RAN node and the target RANnode, the source RAN node sends a Handover Request to the target RANnode through the X2 interface; otherwise, the source RAN node sends aHandover Request to the target RAN node through the S1 interface.

In practice, the details of this step are as follows.

A. If no target RAN node is found in the first column of the interfaceconfiguration table, it indicates that no X2 interface exists betweenthe source RAN node and the target RAN node, and the source RAN nodesends a Handover Request message of the S1 interface directly. If atarget RAN node is found, it indicates that an X2 interface existsbetween the source RAN node and the target neighboring RAN node, and theprocess proceeds to step C.

C. The second row and the rows below it in the interface configurationtable are searched for the “target RAN node” row and the “serving corenetwork node of the source RAN node” row to check the value at theintersection between such a row and the column. If the value is “0,” itindicates that no S1 interface exists between the serving core networknode of the source RAN node and the target RAN node, and the source RANnode sends the Handover Request message of the S1 interface directly. Ifthe value is “1,” it indicates that an S1 interface exists between theserving core network node of the source RAN node and the target RANnode, and the process proceeds to step E.

E. Through an X2 interface, a Handover Request is sent to the target RANnode.

As revealed in the foregoing description, the RAN node in the radionetwork judges whether an S1 interface exists between the RAN node andthe core network according to the S1 interface information of the RANnode and the received S1 interface information, and can select a properinterface accurately and quickly according to the received X2 interfaceinformation. Therefore, the trouble of determining whether the X2interface is available for handover after receiving a Handover Requestin the conventional art is avoided, the handover speed is improved, andthe system load is reduced.

If an S1 interface exists between the serving core network node of thesource RAN node and the target RAN node, and if an X2 link existsbetween the source RAN node and the target RAN node but the X2 linkdisconnected, then the handover fails if the Handover Request is sentthrough the X2 interface directly. Therefore, this step is added tojudge the X2 interface link state first. If the X2 interface link stateis abnormal, the Handover Request is sent through an S1 interface, thusimproving the handover success ratio.

For that purpose, a state value is added on the basis of the S1 or X2interface configuration table to indicate whether the X2 or S1 interfacelinks are normal. Specifically, a parameter may be added to indicatewhether the link is available or existent. Table 5 gives an example.

TABLE 5 S1 or X2 interface configuration table on RAN node 1 corenetwork core network core network RAN node node 1 node 2 node 3 X2 RANnode 2 0 1 2 1 RAN node 3 0 0 1 2

In Table 5, the “X2” column is additional, the “0” value indicates thatno link exists, “1” indicates normal, and “2” indicates link failure.The parameters in Table 5 mean that: The X2 link between RAN node 1 andRAN node 2 is normal; the X2 link between RAN node 1 and RAN node 3 isunavailable; no S1 connection exists between RAN node 2 and core networknode 1, the S1 connection between RAN node 2 and core network node 2 isnormal, and the S1 connection between RAN node 2 and core network node 3is unavailable; and the X2 link between RAN node 1 and RAN node 3 isunavailable.

In other embodiments, the “X2” column may exist in another table. The“X2” column is optional, and is useful in step 201.

When the S1 and X2 interface configuration table in Table 5 is in use,if a target RAN node is found in the first column of the S1 and X2interface configuration table in step A, step B may be performed beforestep C.

B. The first column of the S1 and X2 interface configuration table issearched for the target RAN node. If a target RAN node is found, thevalue in the “X2” column of the S1 and X2 interface configuration tableis looked up. If the X2 link is found to be unavailable, a HandoverRequest message is sent through the S1 interface; otherwise, the processproceeds to step C and then to step D.

D. It is judged whether S1 connection state of the target RAN node isnormal. If the S1 connection state of the target RAN node is normal, aHandover Request is sent through the X2 interface to perform handover;otherwise, a Handover Request message is sent through the S1 interfaceto perform handover.

For example, when source RAN node 1 needs to hand over to target RANnode 2, source RAN node 1 searches Table 5. If the X2 state value is“1,” it indicates that the X2 link is normal. Afterward, the state ofthe core network node connected with RAN node 2 is checked. If the statevalue of core network node 2 is “1,” it indicates that the S1 link isnormal, and the handover is performed through the X2 interface.

In other embodiments, an additional option may be set in the S1 or X2interface configuration table to indicate whether the handover needs tobe performed through the S1 interface or the X2 interface. If the S1 andX2 interface configuration table includes the information about the X2interface between the source RAN node and the target RAN node and theinformation about the S1 interface between the serving core network nodeof the source RAN node and the target RAN node, information is set toindicate that the handover needs to be performed through the X2interface; otherwise, information is set to indicate that the handoverneeds to be performed through the S1 interface.

Alternatively, a simpler S1 interface handover table is generateddynamically on the basis of the S1 or X2 interface configuration table.The S1 interface handover table indicates whether the handover to thetarget RAN node needs to be performed through the S1 interface. The S1interface handover table directly decides whether the S1 interfacehandover process or the X2 interface handover process applies.

The S1 interface handover table falls into the following two types, asdescribed below.

(1) The S1 interface handover table includes MME and S1 interfaceoptions.

In the S1 or X2 interface configuration table, if the S1 interface linkof the serving MME of the source RAN node in Table 1 or Table 5 isalready configured, or if the S1 interface is in the available state,information needs to be set in the S1 interface handover table toindicate that the handover to the target RAN node needs to be performedthrough the S1 interface, as detailed in Table 6.

TABLE 6 Interface handover Table 1 Core network node RAN node 2 RAN node3 MME1 1 1 MME2 0 1

In Table 6, if an S1 interface connection exists between the servingcore network node of the source RAN node and the target RAN node, thevalue of the S1 handover option in the interface handover table is 0,indicating that the handover needs to be performed through the X2interface instead of the S1 interface; otherwise, the value is 1,indicating that the handover needs to be performed through the S1interface. The S1 interface link state may be considered at the sametime. For example, when the S1 interface link state is normal, the valueof the option is 0; otherwise, the value of the option is 1.

For the purpose of handover, this table may be searched for the valuecorresponding to the target RAN node and the serving core network nodeof the source RAN node, and the handover selection is made according tosuch a value directly, without the need of searching the S1 or X1interface configuration table.

Table 6 may be generated by reference to Table 5. After receiving the X2or S1 interface information of the neighboring RAN node, the source RANnode generates an X2 or S1 interface configuration table describedabove, and then generates an S1 interface handover table (as shown inTable 6) according to whether an S1 interface connection exists betweenthe source RAN node and the serving core network node of the source RANnode. That is, if the state indicated in the “core network node” columnin Table 5 is “available,” the handover needs to be performed throughthe X2 interface; otherwise, the handover needs to be performed throughthe S1 interface.

(2) The interface handover table includes only the S1 interface option.

This solution is similar to solution (1), but differs in that: Theinterface handover table includes only the S1 interface option ofdifferent core network nodes between two RAN nodes, and is simpler. Theprinciples are as follows.

It is assumed that all MMEs connected to the same RAN node are in thesame MME pool, and different MME pools are never connected to the sameRAN node. Although an X2 interface exists between two RAN nodes, theyare connected to two MME pools, and the handover between them needs tobe performed through the S1 interface. An interface handover table maybe configured, and such RAN nodes are put into the table. The RAN nodein such an interface handover table needs to hand over through an S1interface.

The interface handover table is set in the following way.

I. The S1 interface information of the target RAN node needs to beobtained first. Through an X2 interface, the target RAN node sends theS1 interface information of the S1 interface between the target RAN nodeand one MME/multiple MMEs/all MMEs to the source RAN node.

II. According to the S1 interface information of the target RAN node andthe S1 interface information of the source RAN node, determining whetherboth the source RAN node and the target RAN node are connected to thesame core network node through an S1 interface.

If the source RAN node and the target RAN node are not connected to thesame core network node through an S1 interface, it is only necessary toset information in the interface handover table to indicate that thehandover to the target RAN node needs to be performed through an S1interface.

After receiving the S1 interface information, the source RAN nodecompares the received S1 interface information with its own S1 interfaceinformation. If one MME/multiple MMEs/all MMEs are the same, itindicates that the source RAN node and the target RAN node are in thesame MME pool; otherwise, it indicates that the source RAN node and thetarget RAN node are not in the same MME pool. The RAN nodes not in thesame MME pool are put into the interface handover table. The S1information includes configuration information, and optionally, linkstate information. As shown in Table 7, RAN node 2 and the source RANnode are not in the same MME pool.

TABLE 7 Interface handover Table 2 Target RAN node State eNB2 1

The communication handover method under the present invention isdetailed below by reference to FIG. 4. As shown in FIG. 4, thecommunication handover process includes at least the following steps.

Step 401: The source RAN node searches the interface handover table.

Step 402: A. If the interface handover table includes a target RAN nodeor the link state is normal, the handover is performed through the S1interface.

B. Otherwise, an attempt is made to hand over through an X2 interface;or, if the link state is abnormal, handover failure is fed backdirectly.

If more state information exists in Table 7, and if the stateinformation indicates link normal, the handover is performed through theS1 interface. This state information is optional.

If the S1 or X2 interface of the RAN node changes, a notification needsto be sent to the neighboring RAN node to let the neighboring RAN nodeupdate the S1 or X2 interface configuration table. Therefore, aninterface information synchronization method in the second embodiment ofthe present invention is put forward. As shown in FIG. 5, the methodincludes the following steps.

Step 501: A judgment is made about whether a condition for initiatinginterface information update is fulfilled.

In this embodiment, a judgment is made about whether the configurationand/or the state of the S1 interface and/or the X2 interface of the RANnode has changed.

Step 502: If the condition for initiating interface information updateis fulfilled, the information about the S1 interface between the RANnode and the core network node, and/or the information about the X2interface between the RAN node and the neighboring RAN node, is sent tothe neighboring RAN node.

When the configuration and/or the state of the S1 interface and/or theX2 interface of the RAN node changes (for example, the RAN node isconnected to another core network node, or the S1 interfaceconfiguration changes, or the address of the X2 interface to theneighboring RAN node changes, or the configuration of both the S1interface and the X2 interface changes), a message is sent to theneighboring RAN node through the X2 interface, where the message carriesthe information about the S1 interface and/or the X2 interface of theRAN node.

The information about the S1 interface and/or the X2 interface of theRAN node may be a special signaling (such as a Config Info message) sentto neighboring RAN node 1, or may be added into another automaticconfiguration message sent to neighboring RAN node 1.

The information about the S1 interface and/or the X2 interface of theRAN node includes: information about the X2 interface between the RANnode and the neighboring RAN node, and/or information about the S1interface between the RAN node and the core network node.

The information about the S1 interface and/or the X2 interface of theRAN node may include the information indicating whether the S1 interfaceand/or the X2 interface between the RAN node and the neighboring RANnode is available, for example, the parameter indicative of the state inthe S1 and X2 interface configuration table in Table 5.

Step 503: The neighboring RAN node receives the S1 and/or X2 interfaceinformation.

Step 504: The neighboring RAN node configures or updates the interfaceinformation of the neighboring RAN node according to the received S1and/or X2 interface information.

In this step, after the neighboring RAN node receives the S1 and/or X2interface information, the neighboring RAN node configures the interfaceinformation if no old interface information exists; or updates theinterface information if old interface information already exists.

The foregoing description reveals that: The RAN node in the radionetwork notifies the latest S1 and/or X2 interface information to theneighboring RAN node automatically when a certain condition isfulfilled. Therefore, the neighboring RAN node keeps aware of the latestX2 interface information and the S1 interface information of theneighboring RAN node. The interface is determined according to thelatest S1 and/or X2 interface information so that the handover operationis performed quickly. The high costs and low efficiency caused by staticconfiguration and manual modification of the RAN node interfaceinformation in the conventional art are overcome, the trouble ofdetermining whether the X2 interface is available for handover in theconventional art is avoided, the handover speed is improved, and thesystem load is reduced.

Besides, the RAN node can also receive the interface information of theneighboring RAN node. The interface information includes: theinformation about the S1 interface between the neighboring RAN node andthe core network node, and/or the information about the X2 interfacebetween the neighboring RAN node and the RAN node.

Therefore, the RAN node not only sends interface information to otherRAN nodes, but also receives interface information from other RAN nodesas a basis for selecting the interface for handover. If the presentinvention is applied to all the RAN nodes in the radio network, the RANnodes exchange the latest S1 and/or X2 interface information, and anyRAN node knows whether to use the X2 interface or the S1 interface forhandover to the target RAN node, thus improving the handover efficiency,avoiding handover failure, and avoiding the interface test operation.

Meanwhile, with the S1 and/or X2 link state being known, the selectionof the handover request is more accurate and the handover success ratiois higher.

It is worthy of attention that when the S1 or S2 configuration of theRAN node changes, all neighboring RAN nodes can be notified through theX2 interface message anytime. After the interface information of theneighboring RAN node is configured or updated, the following operationsare performed.

The S1 interface handover table is obtained through calculationaccording to the interface information of the neighboring RAN node. TheS1 interface handover table includes the information about selecting anS1 or X2 interface for communication handover. In this way, theinterface for handover is determined more quickly, and the speed of thehandover operation is improved.

In the interface information synchronization method provided in theembodiment of the present invention, the judgment about whether thecondition of initiating interface information update is fulfilled instep 501 may be A, B, C, D, E, or F described below:

A. A judgment is made about whether the timer of the S1 and/or X2interface information of the RAN node expires.

All the RAN nodes exchange information with each other periodically. Forexample, a timer is set on the S1 and/or X2 interface information.Moreover, before the interface information is sent, a judgment may bemade about whether the S1 and/or X2 interface information or the linkstate of the RAN node changes; if the interface information or the linkstate changes, the neighboring RAN node is notified through a message;otherwise, the neighboring RAN node is not notified. Alternatively, nojudgment is made, and the interface information is sent upon expiry ofthe timer.

B. A judgment is made about whether a message that the neighboring RANnode requests the S1 and/or X2 interface information is received.

The RAN node may request the latest S1 and X2 interface informationperiodically from the neighboring RAN node through the X2 interface.Upon expiry of the timer of the RAN node, the RAN node requests the X2and S1 interface information from the neighboring RAN node.

C. A judgment is made about whether the X2 handover operation initiatedby the RAN node to the neighboring RAN node fails. For ease ofdescription, the foregoing two nodes are called “source RAN node” and“target RAN node” respectively in the handover process described below.

If the source RAN node searches the S1 and X2 interface configurationtable and decides to perform handover through an X2 interface, thetarget RAN node may find that its own S1 interface link is disconnectedafter sending a Handover Request message. In this case, the target RANnode sends a Handover Failure message to the source RAN node. The S1 andX2 interface configuration table may be sent together with the HandoverFailure message; or the target RAN node gives a cause value, and thesource RAN node requests the new S1 and X2 interface configuration tablefrom the target RAN node. Alternatively, if the S1 interface of thetarget RAN node is unavailable, the core network node sendsconfiguration table information about the S1 interface to the source RANnode.

When the handover operation fails, the S1 and X2 interface informationmay be sent in the following way in step 502.

The Handover Failure response returned to the source RAN node carriesthe S1 and/or X2 interface information of the target RAN node.

Alternatively, the Handover Failure response returned to the source RANnode carries the failure cause, and the source RAN node analyzes thecause value after receiving the failure cause. If the failure cause isradio resource allocation failure, it indicates that the handover fails.If the S1 interface of the target RAN node is not configured or isunavailable, the source RAN node sends a request message, which requiresthe target RAN node to send an S1 and/or X2 interface informationmessage. The target RAN node sends its S1 and/or X2 interfaceinformation to the source RAN node.

Alternatively, the Handover Failure response returned to the source RANnode carries the failure cause. After the source RAN node receives thefailure cause, if the failure cause is lack of an S1 interfaceconnection between the target RAN node and the core network node, thesource RAN node requests the S1 and X2 interface configurationinformation of the target RAN node from the core network node. If thetarget S1 interface configuration recovers to normal, the handover maybe performed through the X2 interface, but the source RAN node is stillunaware of it. The source RAN node sends an S1 interface HandoverRequest to the MME first. After receiving the Handover Request, the MMEfinds that the MME of the target RAN node is the same as that of thesource RAN node. Therefore, the MME may also trigger the source RAN nodeto modify the configuration information of the target RAN node, ornotify the target RAN node to send the S1 interface configurationinformation to the source RAN node. After receiving the S1 interfaceconfiguration information of the target RAN node, the source RAN nodemodifies the X2 and S1 configuration table.

If the source RAN node searches the S1 and X2 interface configurationtable and decides to perform handover through an X2 interface, thetarget RAN node may find that its own S1 interface link is disconnectedafter sending a Handover Request message. In this case, the target RANnode sends a Handover Failure message to the source RAN node. The S1 andX2 interface configuration table may be sent together with the HandoverFailure message; or the target RAN node gives a cause value, and thesource RAN node requests the new S1 and X2 interface configuration tablefrom the target RAN node. Alternatively, if the S1 interface of thetarget RAN node is unavailable, the core network node sendsconfiguration table information about the S1 interface to the source RANnode.

FIG. 6 is a flowchart of interface information synchronization method inan embodiment of the present invention. As shown in FIG. 6, theinterface information synchronization method of the source RAN nodeincludes at least the following steps.

Step 601: The terminal submits a measurement report.

Step 602: After the source RAN node receives the measurement report, ifthe source RAN node decides to hand over and an X2 interface connectionexists, the source RAN node sends a Handover Request to the target RANnode through an X2 interface.

Step 603: If the target RAN node finds that the S1 interface isdisconnected or the radio resource allocation fails, namely, if thehandover fails and the condition for initiating interface informationupdate is fulfilled, the target RAN node returns a Handover Failuremessage to the source RAN node. In this case, the Handover Failuremessage may carry a failure cause value. If the handover fails becauseno S1 interface is configured or the S1 interface is unavailable, theHandover Failure message may carry an S1 and X2 interface configurationtable.

The cause value here may be: lack of configuring the S1 interface of thetarget RAN node, unavailable S1 state, radio resource allocationfailure, NAS error, transmission channel error, or protocol failure.

Step 604: After receiving the Handover Failure message, the source RANnode judges the failure cause according to the cause value. If thehandover fails because no S1 interface is configured or the S1 interfaceis unavailable, and if the Handover Failure message carries aconfiguration table, the source RAN node updates the S1 and X2 interfaceconfiguration table on the source RAN node directly according to theconfiguration table. Otherwise, the process proceeds to step 605 if theHandover Failure message carries no configuration table and indicatesonly the S1 configuration error, and if the cause value is that no S1interface is configured or the S1 interface is unavailable. If thehandover fails due to radio resource allocation failure, the process isended.

Step 605: Through an X2 interface, the source RAN node sends a message(such as Config Info Request message) to the target RAN node, requestingnew X2 and S1 interface information.

Step 606: The information about the S1 interface between the target RANnode and the core network node and/or the information about the X2interface between the target RAN node and the source RAN node is sent tothe source RAN node.

In this step, after receiving the message (such as Config Requestmessage), the target RAN node sends a new configuration informationtable (such as Config Info message) to the source RAN node.

FIG. 7 is a flowchart of interface information synchronization method inanother embodiment of the present invention. As shown in FIG. 7, theinterface information synchronization method of the source RAN nodeincludes at least the following steps:

Step 701: The terminal submits a measurement report.

Step 702: After the source RAN node receives the measurement report, ifthe source RAN node decides to hand over, the source RAN node reads theS1 and X2 interface configuration table and then decides to initiatehandover to the target RAN node through an S1 interface.

Step 703: The MME receives the Handover Request and judges whether thecondition for initiating interface information update is fulfilled. Thatis, the MME judges whether an S1 interface connection exists between thetarget RAN node and the core network node, and between the source RANnode and the core network node. If it is determined that target RAN nodeand the source RAN node are governed by the same MME, the source RANnode is notified to update the S1 configuration information of thetarget RAN node. The process proceeds to step 704 or step 704′, in whichthe S1 and/or X2 interface information of the target RAN node is sent tothe source RAN node.

Step 704: The MME sends the S1 interface information of the target RANnode to the source RAN node, where the S1 interface information may besent in an independent message or carried in the Handover Responsemessage in the handover process; or

Step 704′: The MME sends a message to the target RAN node, thusinitiating the target RAN node to send S1 interface information to thesource RAN node, where the S1 interface information may be sent in anindependent message or carried in the Handover Response message in thehandover process.

Step 705: The source RAN node modifies the X2 and S1 interfaceconfiguration table or the S1 interface handover table.

D. A judgment is made about whether the RAN node is restarted.

E. A judgment is made about whether the Element Manager System (EMS) ofthe RAN node has modified the interface information of the RAN node.

In this case, the process of sending the information about the S1interface and/or the X2 interface to the neighboring RAN node includesthe following steps.

The EMS of the RAN node sends a message that carries the modified S1and/or X2 interface information to the EMS that governs the neighboringRAN node.

FIG. 8 is a flowchart of interface information synchronization method inanother embodiment of the present invention. As shown in FIG. 8, whenthe configuration changes, the change may be notified to the neighboringRAN node Network Management System (NMS) through a message, and theneighboring RAN node NMS notifies the change to the neighboring RANnode. This method includes at least the following steps.

Step 801: A judgment is made about whether a condition for initiatinginterface information update is fulfilled.

If the configuration table of RAN node 1 is changed through modificationof EMS1, a Config Modified message is sent to RAN node 1. Afterreceiving the Config Modified message, RAN node 1 updates the stored S1and X2 interface configuration table. The process proceeds to step 804.

Alternatively, if the configuration table of RAN node 1 changes, theinformation about the S1 interface between RAN node 1 and the corenetwork node and/or the information about the X2 interface between RANnode 1 and the neighboring RAN node are sent to RAN node 2 through anEMS, as detailed below.

Step 802: EMS1 is notified through a Config Request message.

Step 803: After receiving the Config Request message, EMS1 modifies thecorresponding configuration.

Step 804: EMS1 sends a Config Request that carries S1 and/or X2interface information to the neighboring EMS2. EMS2 modifies thecorresponding configuration table according to the S1 and/or X2interface information.

Step 805: EMS2 notifies RAN node 2 through a Config Info message thatcarries the S1 and/or X2 interface information.

Step 806: RAN node 2 modifies the corresponding configuration tableaccording to the S1 and/or X2 interface information.

F. When S1 interface handover occurs and the core network node receivesHandover Request message of the source RAN node, a judgment is madeabout whether the target RAN node and the source RAN node are connectedto the same core network. If such is the case, the S1 interfaceinformation of the target RAN node is sent to the source RAN node; orthe target RAN node is triggered to send S1 interface information to thesource RAN node.

FIG. 9 shows a structure of a radio network in an embodiment of thepresent invention. As shown in FIG. 9, the radio network includes a corenetwork node 710 and neighboring RAN nodes 720, 730, and 740. The RANnode 720 includes: (1) a judging unit 721, adapted to judge whether acondition for initiating interface information update is fulfilled; and(2) a sending unit 722, adapted to: send the information about the S1interface between the RAN node 720 and the core network node 710, and/orthe information about the X2 interface between the RAN node 720 and theneighboring RAN node 730 to the neighboring RAN node 730 if thecondition for initiating interface information update is fulfilled.

The neighboring RAN node 730 includes: (1) a receiving unit 731, adaptedto receive the S1 and/or X2 interface information; (2) a processing unit732, adapted to configure or update the interface information of theneighboring RAN node 730 according to the received S1 and/or X2interface information; and (3) a handover selecting unit 733, adaptedto: search the processing unit 732 for the interface information; iffinding information about the X2 interface between the two neighboringRAN nodes and determining that an S1 interface connection exists betweenthe serving core network node 710 of the source neighboring RAN node 720and the neighboring RAN node 730 which serves as a target node accordingto the S1 interface information, select the X2 interface to initiate ahandover operation; otherwise, select the S1 interface to initiate ahandover operation.

The foregoing description reveals a number of things. The judging unit721 in the radio network judges whether the interface information of theRAN node needs to be updated. If the interface information needs to beupdated, the RAN node notifies the latest S1 and/or X2 interfaceinformation to the neighboring RAN node 730 automatically. Therefore,the neighboring RAN nodes 730 and 740 keep aware of the latest X2interface information and S1 interface information of the neighboringRAN nodes 730 and 740. The interface is determined according to thelatest S1 and/or X2 interface information so that the handover operationis performed quickly. The high costs and low efficiency caused by staticconfiguration and manual modification of the RAN node interfaceinformation in the conventional art are overcome, the trouble ofdetermining whether the X2 interface is available for handover in theconventional art is avoided, the handover speed is improved, and thesystem load is reduced.

The judging unit 721 is adapted to: (1) judge whether the configurationand/or the state of the S1 interface and/or the X2 interface of the RANnode 720 has changed; or (2) judge whether the timer of the S1 and/or X2interface information of the RAN node 720 expires; or (3) judge whethera message that the neighboring RAN node 730 requests the S1 and/or X2interface information is received; or (4) judge whether the X2 handoveroperation initiated by the neighboring RAN node 730 to the RAN node 720fails; or (5) judge whether the RAN node 720 is restarted; or (6) judgewhether the EMS of the RAN node 720 has modified the interfaceinformation of the RAN node 720.

As shown in FIG. 9, a RAN node is disclosed in an embodiment of thepresent invention. The RAN node 720 includes: (1) a judging unit 721,adapted to judge whether a condition for initiating interfaceinformation update is fulfilled; and (2) a sending unit, adapted to:send the information about the S1 interface between the RAN node 720 andthe core network node, and/or the information about the X2 interfacebetween the RAN node 720 and the neighboring RAN node 730 to theneighboring RAN node 730 if the condition for initiating interfaceinformation update is fulfilled.

The RAN node 720 may further receive the interface information of theneighboring RAN node 730. The interface information includes theinformation about the S1 interface between the neighboring RAN node 730and the core network node, and/or the information about the X2 interfacebetween the neighboring RAN node 730 and the RAN node 720. In this case,the RAN node 720 may further include a handover selecting unit (notillustrated in the figure), which is adapted to search for the interfaceinformation. If finding the information about the X2 interface betweenthe RAN node 720 and the neighboring RAN node 730 as well as theinformation about the S1 interface between the serving core network node710 of the RAN node 720 and the neighboring RAN node 730 which serves asa target node, the RAN node 720 selects the X2 interface for initiatinga handover operation; otherwise, select the S1 interface for initiatinga handover operation.

As shown in FIG. 10, a RAN node is disclosed in another embodiment ofthe present invention. The RAN node 730 includes: (1) a receiving unit731, adapted to receive the S1 and/or X2 interface information from theneighboring RAN node 720; (2) a processing unit 732, adapted toconfigure or update the interface information of the neighboring RANnode 720 according to the received S1 and/or X2 interface information;and (3) a handover selecting unit 733, adapted to: search the processingunit 732 for the interface information; if finding the information aboutthe X2 interface between the RAN node 730 and the neighboring RAN node720 as well as the information about the S1 interface between theserving core network node 710 of the RAN node 730 and the neighboringRAN node 720 which serves as a target node, select the X2 interface forinitiating a handover operation; otherwise, select the S1 interface forinitiating a handover operation.

As shown in FIG. 8, a RAN node 830 is disclosed in the third embodimentof the RAN node of the present invention. The RAN node 830 includes: (1)a receiving unit 831, adapted to receive the S1 interface informationfrom the neighboring RAN node; (2) an interface information generatingunit 832, adapted to: judge whether the same core network node existsbetween the RAN node 830 which serves as a source node and theneighboring RAN node which serves as a target node according to the S1interface information of the interface information generating unit 832and the S1 interface information received by the receiving unit 831; andgenerate handover information indicative of handing over to the targetRAN node through an S1 interface if the same core network node does notexist; and (3) a handover selecting unit 833, adapted to: search for thehandover information generated by the interface information generatingunit 832 during the handover; if finding the information about thehandover performed through the S1 interface to the target RAN node,select the S1 interface for initiating a handover operation to theneighboring RAN node; otherwise, select the X2 interface for initiatinga handover operation to the neighboring RAN node.

The first, second, and third embodiments of the RAN node described abovemay be applied to the embodiments of the interface informationsynchronization method and the communication handover method, and cansupport the X2 and S1 interface information synchronization function andthe communication handover function performed according to the X2 and S1interface information. The high costs and low efficiency caused bystatic configuration and manual modification of the RAN node interfaceinformation in the conventional art are overcome, the trouble ofdetermining whether the X2 interface is available for handover in theconventional art is avoided, the handover speed is improved, and thesystem load is reduced.

It is understandable to those skilled in the art that all or part of thesteps of the foregoing embodiments may be implemented by hardwareinstructed by a program. The program may be stored in acomputer-readable storage medium. When being executed, the programperforms these steps: (1) determining whether a condition for initiatinginterface information update is fulfilled; (2) sending information aboutthe S1 interface between the RAN node and the core network node, and/orinformation about the X2 interface between the RAN node and theneighboring RAN node to the neighboring RAN node if the condition forinitiating interface information update is fulfilled; (3) receiving theS1 and/or X2 interface information; and (4) configuring or updating theinterface information of the neighboring RAN node according to thereceived S1 and/or X2 interface information.

Alternatively, when being executed, the program performs these steps.

When handover occurs, the source RAN node reads the stored interfacehandover table, where the interface handover table includes theinformation indicating whether the handover can be performed through theS1 interface to the target RAN node.

The source RAN node performs handover through the S1 interface if theinterface handover table indicates that the handover can be performedthrough an S1 interface to the target RAN node, or else performshandover through the X2 interface.

Alternatively, when being executed, the program performs these steps.

The source RAN node reads interface information when handover occurs,where: the interface information includes the information about whetheran X2 interface exists between the source RAN node and the target RANnode and/or the information about whether an S1 interface exists betweenthe serving core network node of the source RAN node and the target RANnode.

The source RAN node performs handover through an X2 interface if theinterface information indicates that an X2 interface exists between thesource RAN node and the target RAN node and/or an S1 interface existsbetween the serving core network node of the source RAN node and thetarget RAN node, or else performs handover through an S1 interface. Thestorage medium mentioned above may be a ROM/RAM, magnetic disk, compactdisk, and so on.

It is worthy of attention that the judging unit 721, the sending unit722, and the handover selecting unit 733 in the first embodiment of theRAN node of the present invention may be integrated in one computationprocessing module; and the receiving unit 731, the processing unit 732,and the handover selecting unit 733 of the RAN node in the secondembodiment of the present invention may be integrated in one processingmodule, or even all units in an embodiment of the present invention maybe integrated in one processing module.

Further, it is worthy of attention that the judging unit 721, thesending unit 722, and the handover selecting unit 733 in the firstembodiment of the RAN node of the present invention may be hardware orsoftware function modules, and it is the same with the receiving unit731, the processing unit 732, and the handover selecting unit 733 of theRAN node in the second embodiment. The combination of the foregoingunits may be sold or applied as an independent product, or stored in acomputer-readable storage medium.

Detailed above are a synchronization method, a communication handovermethod, a radio network, and a RAN node in an embodiment the presentinvention. Although the invention is described through some exemplaryembodiments, the invention is not limited to such embodiments. It isapparent that those skilled in the art can make various modificationsand variations to the invention without departing from the spirit andscope of the invention.

What is claimed is:
 1. A communication system, comprising: a first radioaccess network (RAN) node; and a second RAN node, wherein the first RANnode is configured to send to the second RAN node, informationindicating the first RAN node belongs to a mobility management entitypool, and wherein the second RAN node is configured to receive theinformation sent by the first RAN node, and to configure or update inthe second RAN node, interface information of the first RAN node, inaccordance with the received information.
 2. The communication systemaccording to claim 1, wherein the first RAN node is configured to sendthe information indicating the first RAN node belongs to the mobilitymanagement entity pool to the second RAN node when at least one of thefollowing occurs: a change in configuration of interface of the firstRAN node, a change in state of interface of the first RAN node, or arestarting of the first RAN node.
 3. The communication system accordingto claim 1, wherein the second RAN node is configured to configure theinterface information of the first RAN node, when the second RAN node iswithout pre-existing interface information of the first RAN node.
 4. Thecommunication system according to claim 1, wherein the second RAN nodeis configured to update the interface information of the first RAN node,when the second RAN node has pre-existing interface information of thefirst RAN node.
 5. The communication system according to claim 1,wherein the first RAN node is configured to send the informationindicating the first RAN node belongs to the mobility management entitypool to the second RAN node in a configuration message through a X2interface.
 6. The communication system according to claim 1, wherein thesecond RAN node is further configured to perform a handover to the firstRAN node through a X2 interface when the second RAN node belongs to themobility management entity pool.
 7. A communication method, comprising:sending, by a first radio access network (RAN) node, to a second RANnode, information indicating the first RAN node belongs to a mobilitymanagement entity pool; receiving, by the second RAN node, theinformation sent by the first RAN node; and configuring or updating inthe second RAN node, by the second RAN node, interface information ofthe first RAN node, in accordance with the received information.
 8. Thecommunication method according to claim 7, wherein the sendingcomprises: sending, by the first RAN node, the information indicatingthe first RAN node belongs to the mobility management entity pool to thesecond RAN node when at least one of the following occurs: a change inconfiguration of interface of the first RAN node, a change in state ofinterface of the first RAN node, or a restarting of the first RAN node.9. The communication method according to claim 7, wherein theconfiguring or updating comprises: configuring in the second RAN node,by the second RAN node, the interface information of the first RAN node,in accordance with the received information, when the second RAN node iswithout pre-existing interface information of the first RAN node. 10.The communication method according to claim 7, wherein the configuringor updating comprises: updating in the second RAN node, by the secondRAN node, the interface information of the first RAN node in accordancewith the received information, when the second RAN node has pre-existinginterface information of the first RAN node.
 11. The communicationmethod according to claim 7, wherein the sending comprises: sending, bythe first RAN node, the information indicating the first RAN nodebelongs to the mobility management entity pool to the second RAN node ina configuration message through a X2 interface.
 12. The communicationmethod according to claim 7, further comprising: performing, by thesecond RAN node, a handover to the first RAN node through a X2 interfacewhen the second RAN node belongs to the mobility management entity pool.13. A radio access network (RAN) node, comprising: a receiver,configured to receive information sent by another RAN node, wherein theinformation indicates the other RAN node belongs to a mobilitymanagement entity pool; and a processor, configured to configure orupdate in the RAN node, interface information of the other RAN node, inaccordance with the information received by the receiver.
 14. The RANnode according to claim 13, wherein the information received by thereceiver is sent by the other RAN node when at least one of thefollowing occurs: a change in configuration of interface of the otherRAN node, a change in state of interface of the other RAN node, or arestarting of the other RAN node.
 15. The RAN node according to claim13, wherein the processor is configured to configure the interfaceinformation of the other RAN node, when the RAN node is withoutpre-existing interface information of the other RAN node.
 16. The RANnode according to claim 13, wherein the processor is configured toupdate the interface information of the other RAN node, when the RANnode has pre-existing interface information of the other RAN node. 17.The RAN node according to claim 13, wherein the receiver is configuredto receive the information which indicates the other RAN node belongs tothe mobility management entity pool in a configuration message through aX2 interface.
 18. The RAN node according to claim 13, wherein theprocessor is further configured to perform a handover to the other RANnode through a X2 interface when the RAN node belongs to the mobilitymanagement entity pool.